//
// Created by q on 2021/1/1.
//
class Solution {
 public:
  int climbStairs(int n) {
    int p = 0, q = 0, r = 1;
    for (int i = 1; i <= n; ++i) {
      p = q;
      q = r;
      r = p + q;
    }
    return r;
  }
};

